Antenna structure



A description of each of the figures of the drawing is as follows, with the broken line matter being for illustrative purposes only and forming no part of the claimed design:

FIG. 1 is an isometric view showing the top, front and left sides of our new design for an antenna structure, shown in full line;

FIG. 2 is a left side elevation view thereof;

FIG. 3 is a rear side elevation view thereof; and,

FIG. 4 is a bottom plan view thereof.

The surfaces of the article not shown in the drawing or described in the specification form no part of the claimed design. 

We claim the ornamental design for the antenna structure, as shown and described. 